All energy systems are working together at any given time. However, depending on intensity and duration of an exercise or a sport, one of the systems is usually dominant. In fact, there is always an overlap among the systems with one being the primary source of energy and the others being the secondary.

Abazar`s Classification for Energy Systems:

The energy system which is the primary source of energy for a specific sport or exercise is called the “Dominant Energy System”, and the secondary energy systems are called the “Non – Dominant Energy Systems”. For example, during a 100 meters dash event or lifting a heavy weight, ATP – PCr is the dominant energy system and glycolysisis the non – dominant energy system, whereas during a 200 meters dash or a 100 meters backstroke swimming, glycolysis is the dominant energy system and ATP – PCr and aerobic systems are the non – dominant energy systems.

For energy systems in different sports, see “Athletic Events” under the section of “Sports”.